Mobile devices like mobile telephones, personal digital assistants and game consoles have been planned small in size and light in weight to become handy and easy to keep with in any situation. One limiting feature in diminishing mobile devices is the usability of a keypad. The popularity of sms-messages (short message service) makes the easy and convenient use of a keypad even more important. Further there are many functions for example in wap (wireless application protocol) devices, which make it inevitable to have a wide range of keys available.
There are devices in the market, which combine a standard mobile phone with personal digital access (pda) features, like touch sensitive screens and larger keyboards. As important as the screen size and the graphical interface are, especially business users value also the capabilities of working with text, accessing menus and sending and receiving messages. Users do a lot of input manually with modern mobile phones. It is rather difficult to make a compromise between a small device and the keyboard big enough to be convenient to use.
In new wap-enabling, smart devices keymats are made bigger to achieve better usability. For example in the Communicator 9210 device manufactured by Nokia Corporation, Espoo, Finland there is a revised keyboard, which includes slightly bigger concave keys than earlier models of the Communicator series. “Communicator” is a registered trademark of Nokia Corporation. In so-called normal mobile phones there are many characters in one button, in order to reduce the actual number of buttons. In personal digital assistant devices, for example in those manufactured by Palm Inc., Santa Clara, Calif., USA, there have been introduced extra tools for writing. An extra tool can be for example a touch screen panel, which accepts a written input on a valid area of a screen panel. Also it is publicly known to input the data by activating drawn pushbuttons or graphical images. Typically this is done by positioning a cursor and activating a selected operation with the aid of a mouse, trackball, pen, wand, stylus, etc. The use of these auxiliary means requires a stable environment and situation.
In the publication EP 651543 there is introduced a personal communicator including a touch sensitive display. This mobile personal communicator includes a casing for a cellular phone, a modem and data processing system. On a touch sensitive display it is possible to choose a next operation by touching a drawn button on a display. Further by touching the screen it is possible to magnify graphical images, such as parts of a fax view and move the images around the display. In this publication the touch screen display comprises a pressure sensitive overlay on a liquid crystal display (LCD).
The publication U.S. Pat. No. 4,899,292 presents a computer coupled to a terminal having a resistive touch screen. As the former one, also this publication deals with images or image formatted data on a display, which are to be magnified. A tactile input is done with the aid of a wand on the touch sensitive screen. The screen detects a voltage signal, which is then converted into coordinates in known manner.
The publication U.S. Pat. No. 6,073,036 illustrates a mobile station with a touch sensitive input means and an automatic symbol magnification operation. A mobile station is provided with a touch sensitive input means, such as a touch sensitive display or a touchpad. The symbols or keys on a touch sensitive keypad can be implemented smaller in size, because the touched key is magnified so that it can be distinguished before selecting it as an input. The magnification is implemented as if there would be a convex lens in the middle of the user and the screen. So the illusion seen by the user is non-linear magnification of the original symbol(s) touched. Subsequent detection of the tactile input and its location can be used for further magnification or for selecting the symbol. In this solution the whole used keypad, which can include for example numbers, alphanumeric characters or special characters, is depicted at a time. The size of one symbol in the screen is dependent on the resolution of the screen. After the magnification, all symbols are still depicted. The pointed, selected one(s) is (are) magnified by the expense of diminishing all the others. The non-linear, lens-like magnification of selected symbol(s) causes the decreasing of the other, non-selected symbols done in proportion to their distance from the selected one(s).